Schematic Reference

Here's how to build a pendulum-controlled clock which can be made really accurate. Retro? - yes, but an interesting project all the same. You'll need a spare quartz clock which must be adapted by first isolating the two pads on the chip which lead to the coil. You then have to connect wires to these pads and feed them out through a hole in the case (see SILICON CHIP, December 1996, p38, for full instructions, or October 2001, p37, for brief notes.) You'll also need a spare battery driven pendulum from another, or the same, clock. As originally used, these pendulums are for appearance only and play no role in timekeeping. The salvaged unit should be mounted on a substantial vertical backboard. You'll find that the pendulum swings pretty fast and it must be slowed down by adding weights near the lower end. However, it's not the mass of a pendulum that controls its rate - instead, it's the distance from the support to the centre of mass that counts.

The aim is to make the pendulum operate so that it takes exactly 1s for a full "to and fro" swing - ie, 0.5s "beats". Fine adjustment on mine was made by adding an adjustable (up and down) weight to the pendulum rod. This consisted of a small G-clamp fabricated from a brass strip and held by a small screw.At the bottom end of the pendulum attach an inverted T-shape aluminium vane, about 10mm wide and as thin as possible. This should be painted black. This vane is used to trigger a photo-interrupter which is attached to the backboard. The lengths of the arms of the "T" are made so that when the pendulum swings one way, the interrupter triggers - ie, the light is no longer blocked. Conversely, when the pendulum swings the other way, the vane must continue to interrupt the light. This means that, with the pendulum swinging in 0.5s beats, we get a short pulse from the photo-interrupter at 1s intervals.

Circuit diagram:

Pendulum-Controlled Clock Circuit Diagram

This pulse is inverted by IC1a and inverted again by IC1b which then clocks IC2, a 4013 flipflop. IC2 alternately produces 1s-long pulses at its pin 12 & 13 outputs. These outputs are then fed to IC1c & IC1d respectively, where they are gated by the short pulses on pin 4 of IC1b. This produces two short pulses to drive the clock in alternate directions at 1s intervals. And that's all you need to drive the clock. Alternatively, this circuit could be a master clock and could be used to drive several slaves, all remaining in time. And model train enthusiasts could drill one or more holes in the vane to make their "railway" clocks run at what ever speed they need.

The circuit can be built on a small piece of strip board. Note that the photo-interrupter should be mounted with the photocell facing the backboard. This minimizes the risk of interference by ambient light. The photo-interrupter is available from Jaycar - Cat.ZD 1901. A footnote for horologists - if you have a clock with a Hipp butterfly escapement, you could rid yourself of the trailing arm and contact arrangement and replace it with a vane and photo-interrupter set so that as the arc of the swing becomes too small, a pulse is missed. This could then be detected by a 555 missing pulse detector circuit which would then energize the impulsing magnet.

Author: A.J Lowe - Copyright: Silicon Chip Electronics

This  circuit disables an alarm clock on Saturdays and Sundays when people like to sleep in but enables normal operation on Mondays to Fridays so that people rise in time for work or school. The core of the circuit is a 4017 decade counter which acts as the day counter and it is used in conjunction with a desk clock which acts the alarm and a watch module with alarm function which provides one clock pulse very day to the 4017. In operation, the watch module feeds a day pulse via transistor Q3 to the clock input of IC1. This has seven outputs connected via day switches (S1-S7) and diodes D3-D9 to Q1 which disables the alarm signal to the speaker via transistor Q2. LEDs1-7 indicate the actual day (if you forget!).

Circuit diagram:

Alarm Clock With Day Selector Circuit Diagram

To set the system, set the desk clock for the correct time and for the desired alarm time (eg, 6’o’clock). The watch module is set to the correct time and its alarm set to midnight. The day counter, IC1, is set to the correct day, as indicated by the LEDs, by pushing switch S12 and closing switch S8 or S9. S8 is normally left open to conserve the battery by leaving the LEDs off. As shown on the circuit, switches S1-S7 are set to sound the alarm on Mondays to Fridays and disable it on Saturday and Sunday. However, you can change the days to suit your work habits.

Author: Rasim Kucalovic - Copyright: Silicon Chip Electronics

This  circuit disables an alarm clock on Saturdays and Sundays when people like to sleep in but enables normal operation on Mondays to Fridays so that people rise in time for work or school. The core of the circuit is a 4017 decade counter which acts as the day counter and it is used in conjunction with a desk clock which acts the alarm and a watch module with alarm function which provides one clock pulse very day to the 4017. In operation, the watch module feeds a day pulse via transistor Q3 to the clock input of IC1. This has seven outputs connected via day switches (S1-S7) and diodes D3-D9 to Q1 which disables the alarm signal to the speaker via transistor Q2. LEDs1-7 indicate the actual day (if you forget!).

Circuit diagram:

Alarm Clock With Day Selector Circuit Diagram

To set the system, set the desk clock for the correct time and for the desired alarm time (eg, 6’o’clock). The watch module is set to the correct time and its alarm set to midnight. The day counter, IC1, is set to the correct day, as indicated by the LEDs, by pushing switch S12 and closing switch S8 or S9. S8 is normally left open to conserve the battery by leaving the LEDs off. As shown on the circuit, switches S1-S7 are set to sound the alarm on Mondays to Fridays and disable it on Saturday and Sunday. However, you can change the days to suit your work habits.

Author: Rasim Kucalovic - Copyright: Silicon Chip Electronics

Add a cheap stopwatch to this circuit to produce an accurate reaction timer. The circuit is wired in parallel with the start/stop button in the watch via a 2.5mm socket, which fits snugly in one corner of the casing. The person conducting the test (the "tester") resets the stopwatch and turns on the reaction timer’s power switch (S3).

The person being tested (the "subject") places his or her fingers near the "STOP" push-button switch (S4). Next, the tester covertly sets a delay time with VR1 and selects either the LED or buzzer alarm via S2. To initiate the sequence, the tester then presses the "START" switch (S1). This triggers 555 timer IC1, which is wired as a monostable. Its output (pin 3) goes high for 2-12 seconds as determined by the setting of VR1. At the end of this delay pin 3 goes low and triggers IC2, another 555 timer in monostable mode.

Circuit diagram:

 An Accurate Reaction Timer Circuit Diagram

The output from IC2 (pin 3) activates the alarm (buzzer or LED) for about 0.5s. After inversion by Q1, it also triggers IC3, another 555 monostable. The positive pulse from IC3 turns on Q2, briefly closing the start/stop switch circuit in the watch. The watch starts to count up. After a short period, the subject reacts to the alarm and pushes the "STOP" button (S4), freezing the stopwatch. The reaction time can then be read off with 1/100th of a second accuracy.

Comparative reaction times could be measured when a subject is: rested or tired, silent or talking, before or after a night out, using a mobile phone, etc. For motoring realism, rig up dummy accelerator and brake pedals, with the brake switch making the stop contact. Or take it to your club and test people as they enter and after they’ve been "steadying their nerves" at the bar.

Author: A. J. Lowe - Copyright: Silicon Chip Electronics

Six timing positions suited to different skin types, Timing affected by sunlight intensity

This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table). When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

Circuit diagram:

A Simple Tan Timer Circuit Diagram

Parts:

R1 = 47K - 1/4W Resistor
R2 = 1M - 1/4W Resistor
R3 = 120K - 1/4W Resistors
R4 = Photo resistor (any type)
R5 = 120K - 1/4W Resistors
C1 = 10µF - 25V Electrolytic Capacitors
C2 = 220nF - 63V Polyester Capacitor
C3 = 10µF - 25V Electrolytic Capacitors
D1 = 1N4148 - 75V 150mA Diodes
D2 = 1N4148 - 75V 150mA Diodes
Q1 = BC337 - 45V 800mA NPN Transistor
B1 = 3V Battery (two 1.5V AA or AAA cells in series)
IC1 = 4060 - 14 stage ripple counter and oscillator IC
IC2 = 4017 - Decade counter with 10 decoded outputs IC
SW1 = 2 poles 6 ways Rotary Switch (see notes)
SW2 = SPST Slider Switch
BZ1 = Piezo sounder (incorporating 3KHz oscillator)

Notes:

• Needing only one time set suitable for your own skin type, the rotary switch can be replaced by hard-wired links.
• A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time when the device is off, or the ICs could be damaged.

Source : www.redcircuits.com

Pushbutton activated, Very simple circuitry

This device is a simple timer, allowing to keep on the headlights of your vehicle for about 1min. and 30sec., e.g. when accessing some dark place, without the necessity of coming back to switch-off the lights. Pushing on P1 allows C1 charging to full 12V battery supply. Therefore Q1 is driven hard-on, driving in turn Q2 and its Relay load. The headlights are thus activated by means of the Relay contact wired in parallel to the vehicle's headlights switch. RL1 remains activated until C1 is almost fully discharged, i.e. When its voltage falls below about 0.7V. The timing delay of the circuit depends by C1 and R1 values and was set to about 1min. and 30sec.

In practice, due to electrolytic capacitors wide tolerance value, this delay will vary from about 1min. and 30sec. to 1min. and 50sec. An interesting variation is to use the inside lamp as a command source for the timer. In this way, when the door is opened C1 is charged, but it will start to discharge only when the door will be closed, substituting pushbutton operation. To enable the circuit acting in this way, simply connect the cathode of a 1N4002 diode to R1-C1 junction and the anode to the "live" lead of the inside lamp. This lead can be singled-out using a voltmeter, as it is the lead where a 12V voltage can be measured in respect to the vehicle frame when the lamp is on.

Circuit diagram:

Car Headlights Timer Circuit Diagram

Parts:

R1 = 4.7K - 1/4W Resistor
R2 = 1K - 1/4W Resistors
R3 = 1K - 1/4W Resistors
C1 = 100µF - 25V Electrolytic Capacitor (See Notes)
D1 = 1N4002 - 100V 1A Diode
Q1 = BC547 - 45V 100mA NPN Transistor
Q2 = BC327 - 45V 800mA PNP Transistor
P1 = SPST Pushbutton
RL1 = Relay with SPDT 10A min. switch
Coil Voltage 12V. Coil resistance 150-600 Ohms

Notes:

• The Relay contact must be rated at 10A or more.
• Time-delays obtained trying different tolerance electrolytic capacitors for C1:
• 100µF = 1'30" to 1'50"
• 47µF = 0'45" to 1'05"
• 220µF = 3'15" to 4'15"

Source : www.extremecircuits.net

This circuit enables the on/off times of a 555 timer to be independently varied over a wide range. This is not possible with a conventional 555 circuit with the RC network being charged from the positive supply rail and discharged via pin 7. Instead, the capacitor at pins 2 & 6 of IC1 is charged and discharged from the output at pin 3. Furthermore, the charging and discharging circuits are different, being isolated by diodes D1 & D2.

Circuit diagram:

555 Timer Circuit Diagram With Variable On/Off Times

Therefore the capacitor at pins 2 & 6 is charged via diode D2 and trimpot VR2 and discharged via D1 and trimpot VR1. With this arrangement you can have very long on times combined with very short off times and vice versa, or you can adjust the duty cycle to exactly 50% and so on. This circuit also employs a second 555 timer (IC2) as an inverter so that complementary pulses are available, if required. If not, delete IC2.

Author: A. Davies - Copyright: Silicon Chip Electronics

The quartz clocks which have dominated time-keeping for the past 20 years or so have one problem: their errors, although slight, are cumulative. After running for several months the errors can be significant. Sometimes you can correct these if you can slightly tweak the crystal frequency but otherwise you are forced to reset the clock at regular intervals. By contrast, mains-powered synchronous clocks are kept accurate by the 50Hz mains distribution system and they are very reliable, except of course, when a blackout occurs. This circuit converts a quartz clock to synchronous mains operation, so that you can have at least one clock in your home which shows the time. First, you need to obtain a quartz clock movement and disassemble it down to the PC board. For instructions on how to do this, see the article on a "Fast Clock For Railway Modellers" in the December 1996 issue of SILICON CHIP. Then isolate the two wires to the clock coil and solder two light duty insulated hookup wires to them (eg, two strands of rainbow cable). Drill a small hole in the clock case and pass the wires through them. Then reassemble the clock case.

Circuit diagram:

A Synchronous Clock Circuit Diagram

To test the movement, touch the wires to the terminals of an AA cell, then reverse the wires and touch the cell terminals again. The clock second hand should advance on each connection. The circuit is driven by a low voltage AC plug pack. Its AC output is fed to two bridge rectifiers: BR1 provides the DC supply while BR2 provides positive-going pulses at 100Hz to IC1a, a 4093 NAND Schmitt trigger. IC1a squares up the 100Hz pulses and feeds them to the clock input of the cascaded 4017 decade counters. The output at pin 12 of IC3 is 1Hz. This is fed to IC4, a 4013 D-type flipflop, which is connected so that its two outputs at pins 12 & 13 each go positive for one second at a time. As these pulses are too long to drive the clock movement directly, the outputs are each fed to 4093 NAND gates IC1b & IC1c where they are gated with the pin 3 signal to IC4. This results in short pulses from pins 3 & 10 of IC1 which drives the clock via limiting resistor R1. The value of R1 should be selected on test, allowing just enough current to reliably drive the clock movement.

Author: A. J. Lowe - Copyright: Silicon Chip

Suitable for battery-operated devices, Fixed 35 minutes delay

This timer was designed mainly to switch off a portable radio after some time: in this way, one can fall asleep on the sand or on a hammock, resting assured that the receiver will switch off automatically after some time, saving battery costs.

Circuit operation:

R1 and C1 provide a very long time constant. When P2 is momentarily closed, C1 discharges and the near zero voltage at its positive lead is applied to the high impedance inputs of the four gates of IC1 wired in parallel. The four paralleled gate outputs of the IC go therefore to the high state and the battery voltage is available at Q1 Emitter. When P2 is released, C1 starts charging slowly through R1 and when the voltage at its positive lead has reached about half the battery voltage, the IC gate outputs fall to zero, stopping Q1.

This transistor can directly drive a portable radio receiver or different devices drawing a current up to about 250mA. Connecting a Relay across the Emitter of Q1 and negative ground, devices requiring much higher voltage and current operation can be driven through its contacts. Pushing on P2 for 1 to 5 seconds, the circuit starts and then will switch off after about 35 minutes. This time delay can be varied by changing R1 and/or C1 values. P1 will stop the timer if required.
LED D1 is optional and can be useful to signal relay operation when the load is placed far from the timer.

Circuit diagram:

Long Delay Timer Circuit Diagram

Parts:

R1_________10M 1/4W Resistor
R2_________4K7 1/4W Resistor
R3_________1K 1/4W Resistor (Optional, see Text)
C1_________220µF 25V Electrolytic capacitor
D1_________LED any type and color (Optional, see Text)
D2_________1N4148 75V 150mA Diode (Optional, see Text)
IC1_________4011 Quad 2 Input NAND Gate CMos IC (See Notes)
Q1_________BC337 45V 800mA NPN Transistor
P1,P2______SPST Pushbuttons
RL1________Relay with SPDT 2A @ 230V switch (Optional, see Text)
Coil Voltage 12V - Coil resistance 200-300 Ohm
Notes:

• A 4011 Quad 2 Input NAND Gate was used for IC1, but many other CMos gates or inverter arrays can be used in its place, e.g. 4001, 4002, 4025, 4012, 4023, 4049, 4069. With these devices, all inputs must be tied together and also all outputs, as shown in the Circuit diagram.
• The operating voltage of this circuit should lie in the 6 - 12V range.

Source: www.RedCircuits.com

Using this design, you can construct an electromagnetically impulsed pendulum clock with a 1-second beat. On the prototype, the pendulum rod is 115cm long with a bob adjusted to make it beat every second. It is suspended on a short piece of mainspring from a watch, which is attached to a vertical backboard with a 6mm screw. The rod extends some 15cm below the bob and is fitted with large washes at the lower end. Note that for a pendulum to beat in seconds, there must be 99.4cm distance between the support and the centre of mass of the pendulum. Between the bob and the lower end is a 5mm wide white reflector facing back. Below the rod and 15mm to the left is the impulse solenoid, with a core but no actuator attached. The circuit comprises of four parts: (1) the sensor; (2) the counter and solenoid driver; (3) the clock driver; and (4) the clock.

The sensor is built on its own small piece of strip board and is located on the centre line of the backboard behind the reflector. It utilises a Sharp IS471F infrared modulated detector (Farnell cat. 414-2860) to eliminate interference from external light sources. The infrared emitter (IRLED1) must be mounted near to the detector (IRDET1) but be masked from it. The emitter radiates a coded signal toward the reflector. As the pendulum passes the centre line it reflects the signal back to the detector, which then gives a negative-going output pulse on pin 2. This makes the surface-mount LED (LED1) flash once. It also sends a signal to the counter and clock driver circuits on the main circuit board. Pulses from the sensor are fed into IC1, a 4020 14-stage ripple counter. The counter’s output (pin 6) goes high every 128 counts (seconds). These long duration pulses are inverted by transistor Q1 and differentiated by the 10nF capacitor and 22kO resistor, providing a narrow trigger pulse for a 7555 CMOS timer (IC2).

Circuit diagram:

Experimental Pendulum Clock Circuit Diagram

The 7555 is wired as a monostable, driving the base of transistor Q3 with a relatively short pulse width suitable for energising the impulse solenoid. LED2 flashes in unison with solenoid pulses, and can be mounted right on the solenoid as a visual aid. Pushbutton switch S2 is used to provide gentle starting pulses to get the pendulum swinging smoothly at the outset. Switch S1 resets the counter to zero. With this arrangement, the pendulum is set swinging and when it is to the left of centre, S1is pushed. Thus, the pendulum moves right to left on even numbered counts. At the 128th count, the solenoid gives a shot pull to the left just as the pendulum is passing through the centre line and moving right to left. The distance of the solenoid below the pendulum is adjusted so that it does not jerk the pendulum but adds a gentle nudge. The clock driver circuit also derives its timing from the output of the sensor. Negative-going pulses from the sensor are inverted by Q4 before being fed into a 4013 flipflop. On the output side, pins 12 & 13 go high in turn for one second.  These pulses are too long to directly drive the clock coil, so they’re logically "anded" with the short pulses from the sensor using two gates of a 4093 NAND Schmitt trigger (IC4).

The outputs from these gates then drive an adapted quartz clock movement. A suitable clock can be made from a standard quartz movement by isolating the coil and removing the battery. See SILICON CHIP, Dec. 1996, page 38 for full instructions or October 2001 page 37 for brief notes. This is an experimental clock so you may have to try various solenoids to find one that works for you. If necessary, the solenoid pulse duration can be changed by varying IC2’s timing components. If the suspension is too stiff, try impulsing at 64 beats from pin 4 of IC1, but note that the aim is to get the freest pendulum movement possible. The Synchronome and Hipp clocks were impulsed at 30-second intervals, so your clock could be even better. In the prototype, the reflector was made from the back of an adhesive cable clip snapped on to the pendulum rod. The white back was masked to give a 5mm wide central vertical strip, giving clean, short pulses as the pendulum passes. Current drain is several milliamps, so the prototype was powered from an SLA battery fed from a float charger. A pendulum beating in seconds is called a Royal pendulum. Its length is the same as one in a typical long case (grandfather) clock.

Author: A. J. Lowe - Copyright: Silicon Chip Electronics

CMOS circuits are known for their low current consumption. This is particularly important for battery-powered circuits. Unfortunately, oscillators often require quite a bit of current. We therefore propose this oscillator circuit that has a very low current consumption (about 3 µA). The circuit is powered from a type LM334Z current source. The current has been set with R4 to about 3 µA.

Circuit diagram:

Thrifty 2Hz Clock Circuit diagram

This is sufficient to power IC1 and the oscillator circuit around X1. The oscillator generates, with the aid of a cheap watch crystal and a few surrounding parts, a signal that is subsequently applied to the divider in the 4060 and results in a frequency of 2 Hz at pin 3 (output Q13). The level of the output pulses is a lot lower than the nominal 5-V power supply voltage (IC1 is after all powered from a current source with very low current). That is why the signal on pin 3 of IC1 is amplified and inverted by T1. IC3a finally turns it into a proper square wave with acceptably steep edges.

Source : www.extremecircuits.net

Beeps 7.5 seconds after a preset time, Adjustable time settings: 15s. 30s. 1min. & others

This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it is a modern substitute for the old sandglass. Useful also for time control when children are brushing teeth (at least two minutes!), or in the kitchen, and so on.

Circuit diagram:

 Timed Beeper Circuit Diagram

Parts:

R1 = 220R
R2 = 10M
R3 = 1M
R4 = 10K
R5 = 47K
C1 = 100nF-63V
C2 = 22µF-25V
D1 = 1N4148
D2 = 3mm. Red LED
Q1 = BC337

P1 = SPST Pushbutton (Start)
P2 = SPST Pushbutton (Reset)
PS = Piezo sounder (incorporating 3KHz oscillator)
B1 = 3V Battery (2 AA 1.5V Cells in series)
IC1 = CD4081 Quad 2 input AND Gate IC
IC2 = CD4060 14 stage ripple counter and oscillator IC
SW1 = 4 ways Switch (See notes)

Circuit operation:
Pushing on P1 resets IC2 that start oscillating at a frequency fixed by R3 & C1. With values shown, this frequency is around 4Hz. LED D2, driven by IC1A & B, flashing at the same oscillator frequency, will signal proper circuit operation. SW1 selects the appropriate pin of IC2 to adjust timing duration:

• Position 1 = 15 seconds
• Position 2 = 30 seconds
• Position 3 = 1 minute
• Position 4 = 2 minutes

When the selected pin of IC2 goes high, IC1C drives Q1 and the piezo sounder beeps intermittently at the same frequency of the LED. After around 7.5 seconds pin 4 of IC2 goes high and IC1D stops the oscillator through D1. If you want to stop counting in advance, push on P2.

Notes:

1. SW1 can be any type of switch with the desired number of ways. If you want a single fixed timing duration, omit the switch and connect pins 9 & 13 of IC1 to the suitable pin of IC2.
2. The circuit's reset is not immediate. Pushing P2 forces IC2 to oscillate very fast, but it takes some seconds to terminate the counting, especially if a high timer delay was chosen and the pushbutton is operated when the circuit was just starting. In order to speed the reset, try lowering the value of R5, but pay attention: too low a value can stop oscillation.
3. Frequency operation varies with different brand names for IC2. E.g. Motorola's ICs run faster, therefore changing of C1 and/or R3 values may be necessary.
4. You can also use pins 1, 2, 3 of IC2 to obtain timings of 8, 16 and 32 minutes respectively.
5. An on-off switch is not provided because when off-state the circuit draws no significant current.

Source :www.extremecircuits.net

30 minutes operation, Blinking LED signals 6 last minutes before turn-off

The purpose of this circuit is to power a lamp or other appliance for a given time (30 minutes in this case), and then to turn it off. It is useful when reading at bed by night, turning off the bedside lamp automatically in case the reader falls asleep... After turn-on by P1 pushbutton, the LED illuminates for around 25 minutes, but then it starts to blink for two minutes, stops blinking for two minutes and blinks for another two just before switching the lamp off, thus signaling that the on-time is ending. If the user want to prolong the reading, he/she can earn another half-hour of light by pushing on P1. Turning-off the lamp at user's ease is obtained by pushing on P2.

Circuit diagram:

 A Bedside Lamp Timer Circuit Diagram

Parts:

Resistors
R1 = 1K
R2 = 4K7
R3 = 10M
R4 = 1M
R5 = 10K

Capacitors
C1 = 470µF-25V
C2-C4100nF-63V

Semiconductors
C1 = 470µF-25V
C2-C4 = 100nF-63V
D1-D4 = 1N4002
D5 = 5mm. Red LED
IC1 = CD4012
IC2 = CD4060
Q1 = BC328
Q2 = BC547

Miscellaneous
P1,P2 = SPST Pushbuttons
T1 = 9+9 Volt Secondary 1VA Mains transformer
RL1 = 10.5V 470 Ohm Relay with SPDT 2A 220V switch
PL1 = Male Mains plug
SK1 = Female Mains socket

Circuit operation:
Q1 and Q2 form an ALL-ON ALL-OFF circuit that in the off state draws no significant current. P1 starts the circuit, the relay is turned on and the two ICs are powered. The lamp is powered by the relay switch, and IC2 is reset with a positive voltage at pin 12. IC2 starts oscillating at a frequency set by R4 and C4. With the values shown, pin 3 goes high after around 30 minutes, turning off the circuit via C3. During the c6 minutes preceding turn-off.

The LED does a blinking action by connections of IC1 to pins 1, 2 & 15 of IC2. Blinking frequency is provided by IC2 oscillator at pin 9. The two gates of IC1 are wired in parallel to source more current. If required, a piezo sounder can be connected to pins 1 & 14 of IC1. Obviously, timings can be varied changing C4 and/or R4 values.

Source : www.extremecircuits.net